Gerry Adams, president of Sinn Fein, the political wing of the Irish Republican Army, said Sunday that he could not guarantee that the IRA would agree to disarm during the negotiations in the new Northern Ireland Assembly.

Protestant and Catholic leaders opened discussions Monday in Belfast on how to share power in a new government for Northern Ireland.Adams' hard-line statement contrasted with remarks he made last week on the eve of President Clinton's visit to Ireland, when he emphasized that sectarian warfare was a thing of the past.

But on Sunday Adams returned to the intransigent position of the IRA on disarmament, which has been that it is a matter for the IRA alone to decide. The IRA has an estimated 100 tons of machine guns, mortars and Semtex explosive. The outlawed overwhelmingly Catholic organization has been observing a cease-fire for 14 months.

Disarmament is likely to delay the work of the Assembly, a mixture of Roman Catholic and Protestant politicians.

But David Trimble, leader of the Protestant Ulster Unionist Party and First Minister of the Assembly, sounded unusually positive Sunday about the prospects for an eventual IRA disarmament.